Multi-Portion Radio Transmissions

ABSTRACT

Techniques are disclosed relating to generating and receiving radio frames with multiple portions that have different encoding schemes. An apparatus may include one or more processing elements configured to receive, via a wireless radio, wireless data that includes a plurality of portions that each include multiple orthogonal frequency-division multiplexing (OFDM) symbols. Different ones of the portions have different frequency transform sizes and different sampling rates. The wireless data may also include control data that indicates the frequency transform sizes and sampling rates for the ones of the portions. The apparatus may select, based on the control data and a determined velocity of the apparatus, one or more but not all of the plurality of portions and may decode the selected one or more portions to determine data represented by the OFDM symbols in the selected one or more portions. Different portions of the wireless data may be adapted for decoding by devices moving at different maximum velocities.

This application is a continuation of U.S. patent application Ser. No.15/247,198, filed on Aug. 25, 2016, which is a continuation of U.S.patent application Ser. No. 14/805,004, filed on Jul. 21, 2015, now U.S.Pat. No. 9,438,459 issued on Sep. 6, 2016, which claims the benefit ofU.S. Provisional Application No. 62/034,626, filed on Aug. 7, 2014; thedisclosures of all of which are incorporated by reference herein intheir respective entireties.

The claims in the instant application are different than those of theparent application or other related applications. The Applicanttherefore rescinds any disclaimer of claim scope made in the parentapplication or any predecessor application in relation to the instantapplication. The Examiner is therefore advised that any such previousdisclaimer and the cited references that it was made to avoid, may needto be revisited. Further, any disclaimer made in the instant applicationshould not be read into or against the parent application or otherrelated applications.

FIELD OF THE DISCLOSURE

The present disclosure relates to the field of wireless communication,and more particularly, to mechanisms for dynamically constructing OFDMphysical transport frames, to enable flexibility in configuration oftransmissions in broadcast networks.

DESCRIPTION OF THE RELATED ART

In today's world, many electronic devices rely upon wirelessconnectivity for the reception of data from other connected devices. Ina typical wireless deployment, there may be one or more wireless accesspoints that transmit data, and one or more devices that receive datafrom the wireless access point(s).

In such a scenario, different devices may have different propagationchannel characteristics, and these may affect their wireless datareception from the same wireless access point. For example, a devicethat is near the wireless access point and/or that has a fixed location(or is slowly moving) may have better propagation channel conditionsthan would a device that is moving at a high velocity and/or that isfurther away from the wireless access point. The first device may fallinto a group of devices able to receive data encoded and transmittedwith one set of parameters (such as a high Forward Error Correction(FEC) code rate, a high modulation level, and/or a smaller subcarrierspacing in an Orthogonal Frequency Division Multiplexing (OFDM) system),while the second device may fall into a group of devices that need datato be encoded and transmitted with a second set of parameters (such as alow FEC code rate, a low modulation level, and/or a wider subcarrierspacing in an OFDM system).

There are many scenarios where a large number of devices may all wish toreceive identical data from a common source. One such example isbroadcast television, where a large number of television sets in varioushomes all receive a common broadcast signal conveying a program ofinterest. In such scenarios, it is significantly more efficient tobroadcast or multicast the data to such devices rather than individuallysignaling the same data to each device. However, programs with differentquality levels (e.g. high definition video, standard definition video,etc.) may need to be transmitted to different groups of devices withdifferent propagation channel characteristics. In other scenarios, itmay be desirable to transmit device-specific data to a particulardevice, and the parameters used to encode and transmit that data maydepend upon the device's location and/or propagation channel conditions.

As described above, different sets of transmitted data may need to betransmitted with different encoding and transmission parameters, eithersimultaneously or in a time-multiplexed fashion (or both). The amount ofdata to be transmitted in a particular data set and/or the encoding andtransmission parameters for that data set may vary with time.

At the same time, the demand for high-speed wireless data continues toincrease, and it is desirable to make the most efficient use possible ofthe available wireless resources (such as a certain portion of thewireless spectrum) on a potentially time-varying basis.

SUMMARY

Modern and future high-speed wireless networks should be designed forefficient handling of a variety of deployment scenarios. The presentpatent discloses mechanisms that enable broad flexibility in wirelessdata delivery, to support services in a full range of deploymentscenarios, which might include, but are not limited, to the following:

receiver mobility (e.g. fixed, nomadic, mobile);

cell size (e.g. macro, micro, pico);

single or multiple frequency networks (SFN or MFN);

multiplexing of different services; and/or

bandwidth sharing.

In one set of embodiments, a method for receiving or generating a frameof wireless data may be implemented as follows.

In some embodiments, a computing device (e.g., corresponding to a basestation or a broadcast gateway) receives or generates a payload regionfor a frame of wireless data. In some embodiments, the payload regionincludes a plurality of partitions that each include multiple orthogonalfrequency-division multiplexing (OFDM) symbols. In some embodiments,different ones of the partitions have different frequency transform(e.g., Fast Fourier Transform (FFT)) sizes for the OFDM symbols in theones of the partitions. These different frequency transform sizes may beadapted for decoding by mobile devices at different velocities (e.g.,one partition may be adapted for mobile devices carried by pedestriansand another for mobile devices carried in vehicles). For example,smaller FFT sizes may be adapted for decoding by faster-moving devices.In various embodiments, any number of different partitions adapted fordecoding by mobile devices in different velocity ranges may be included.Additional velocity ranges may include ranges corresponding to nomadicdevices, ranges corresponding to aircraft, etc.

In some embodiments, different ones of the partitions may have differentcyclic prefix sizes, which may be selected to maintain a desired cellsize. Partitions with different cyclic prefix sizes may be adapted forreceiving devices having different expected delay spreads, for example.

In some embodiments, the computing device broadcasts the frame ofwireless data, including the payload region. In other embodiments (e.g.,when the computing device is a gateway), the device may transmit thepayload region to a base station which may then broadcast the frame ofwireless data.

In some embodiments, the operations also include generating partitiondata for the frame of wireless data that indicates the FFT size and/orthe cyclic prefix size for each of the partitions.

In some embodiments, each of the partitions includes a corresponding setof overhead resource elements (such as reference symbols). In theseembodiments, the operations may also include scheduling symbol data fromone or more service data streams to each of the partitions after havingreserved the overhead resource elements within the frame.

In some embodiments, the frame may be partitioned according to one ormore other factors in addition to (or, as an alternative to) theabove-described partitioning according to the expected user mobility anddesired cell coverage as determined by FFT size and cyclic prefix size,e.g., factors such as:

-   -   data rate, wherein different partitions have different data        rates, e.g., high data rate vs. low data rate (along the lines        of Internet of Things), with a lower duty cycle for low power        reception;    -   tight vs. loose clustering of transport blocks (e.g., Physical        Service Data Channels (PSDCHs)) within each partition where time        diversity may be sacrificed in the interest of allowing a low        power device to wake up, consume the data it needs, and then go        back to sleep;    -   frequency partitioning, which may allow band edges to be coded        more robustly using a lower modulation order to permit band        shaping or other interference mitigation techniques; and/or    -   broadcast content, such as local v. regional programming, which        may be broadcast using different partitions.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the disclosed embodiments may be obtained whenthe following detailed description is considered in conjunction with thefollowing drawings.

FIG. 1A illustrates one embodiment of a broadcast network including aplurality of base stations.

FIG. 1B illustrates one embodiment of an Orthogonal Frequency DivisionMultiplexing (OFDM) symbol with both a cyclic prefix and a usefulportion.

FIG. 1C is a table showing the cyclic prefix lengths (in number ofsamples) and corresponding ranges (in km) for various example cyclicprefix lengths specified relative to (as a percentage of) the usefulportion of each OFDM symbol.

FIG. 2 illustrates an overview of a possible frame structure.

FIG. 3 illustrates two examples of Physical Partition Data CHannel(PPDCH) time multiplexing with distinct time separation of the PPDCHs.

FIG. 4 shows an exemplary frame whose Physical Frame Data CHannel(PFDCH) includes: a first partition 322 of length 660 ms and 8K FFTsize; and a second partition 326 of length 330 ms and 64K FFT size.

FIG. 5 illustrates the relationship between different physical channelsfor carrying payload data, according to some embodiments.

FIG. 6 illustrates a special case where two PPDCHs each include only onePSDCH.

FIG. 7 illustrates a special case where a PFDCH includes only one PPDCH.

FIG. 8 illustrates useful subcarriers within an OFDM symbol, accordingto one embodiment.

FIG. 9 illustrates an example of PPDCH frequency multiplexing, accordingto one embodiment.

FIG. 10 illustrates the layout of logical resources within a PPDCH,according to one embodiment.

FIG. 11 illustrates logical stripes and logical subbands within a PPDCH,according to one embodiment.

FIG. 12 illustrates a mapping of virtual stripes belonging to a virtualsubband to logical stripes belonging to a logical subband, according toone embodiment.

FIG. 13 illustrates an example rotation and mapping of virtual stripesto logical stripes, according to one embodiment.

FIG. 14 illustrates an example rotation and mapping of logical stripesto virtual stripes, according to one embodiment.

FIG. 15 illustrates an example of mapping a Physical Service DataCHannel (PSDCH) to virtual resources of a PPDCH, according to oneembodiment.

FIG. 16 illustrates an example of concatenated PFDCH, PPDCH, and PSDCHdescriptors for communication to a receiver, according to oneembodiment.

FIG. 17 illustrates one embodiment of a method for receiving orgenerating a payload region for a frame of wireless data, according tosome embodiments.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and are herein described in detail. It should beunderstood, however, that the drawings and detailed description theretoare not intended to limit the invention to the particular formdisclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE EMBODIMENTS List of Potentially RelevantAcronyms ATS: Auxiliary Termination Symbols BG: Broadcast Gateway BS:Base Station CP: Cyclic Prefix CRC: Cyclic Redundancy Check DC: DirectCurrent FEC: Forward Error Correction FFT: Fast Fourier Transform IFFT:Inverse Fast Fourier Transform LDPC: Low Density Parity Check MAC:Medium Access Control NIFN: Multi-Frequency Network MHz: Mega HertzOFDM: Orthogonal Frequency Division Multiplexing PDU: Protocol Data Unit

PHY PHYsical layer

PFDCH: Physical Frame Data CHannel PPDCH: Physical Partition DataCHannel PSDCH: Physical Service Data CHannel QAM: Quadrature AmplitudeModulation RS: Reference Symbols SFN: Single Frequency Network BroadcastNetwork Architecture

In some embodiments, a broadcast network may be configured as shown inFIG. 1A. In the illustrated embodiment, the broadcast network includes abroadcast gateway (BG) 110 coupled to a plurality of base stations120A-N and an operator system (Op) 130. Broadcast gateway 110 may coupleto the base stations through any of a variety of communication media.For example, in one embodiment, the broadcast gateway may couple to thebase stations via the Internet, or more generally, via a computernetwork. Each base station 120 is configured to wirelessly transmitinformation to one or more user devices. (Each user device (UD) isdenoted by a solid block circle, in the illustrated embodiment.) Some ofthe user devices may be fixed devices such as televisions and desktopcomputers. Other ones of the user devices may be nomadic devices such astablet computers or laptop computers. Other ones of the user devices maybe mobile devices such as mobile phones, automobile-based devices,aircraft-based devices, etc.

An operator of the broadcast network may access the broadcast gateway(e.g., via the Internet), and provide network configuration or operatinginformation to the gateway. This information may include:

-   -   an expected distribution of user device mobility for one or more        of the base stations;    -   the cell size of one or more of the base stations;    -   a selection of whether the broadcast network or a subset of the        network is to be operated as a single frequency network (SFN) or        a multi-frequency network (MFN);    -   a specification of how different services (e.g., television        content streams) are to be assigned to different types of user        devices;    -   identification of portions of bandwidth the broadcast network        will not be using over corresponding periods of time.        The broadcast gateway 110 may determine transmission control        information for one or more base stations 120 of the broadcast        network based on the network configuration or operating        instructions. For a given base station, the broadcast gateway        may determine the following attributes for frames of wireless        data to be broadcast: number of partitions, sizes of the        partitions, FFT size for each partition, and/or cyclic prefix        size for each partition. The broadcast gateway may send the        transmission control information to the base stations so the        base stations may construct and transmit frames according to the        transmission control information. In other embodiments, the        gateway may itself generate frames to be transmitted by each        gateway and send the frames to the base stations. In yet other        embodiments, the gateway may generate low level instructions        (e.g., physical layer instructions) for the construction of        frames to the base stations, and send those instructions to the        base stations, which may simply generate frames based on the        instructions.

OFDM Symbols and FFT/IFFT Sizes

Orthogonal Frequency Division Multiplexing (OFDM) systems typically usean Inverse Fast Fourier Transform (IFFT) operation at the transmitter toconvert frequency domain data to the time domain for transmission, and aFast Fourier Transform (FFT) operation at the receiver to convertreceived time domain values back to the frequency domain in order torecover the originally transmitted data. In the following text, the termFFT is generally used, but the parameters described correspond to thefrequency and time dimensions for both the FFT and IFFT operations.Thus, the term “FFT size” may refer to the size of either an IFFT or anFFT.

For illustration purposes, an example base sampling rate of Fs=12.288MHz is generally used herein. This is not intended to be limiting, andother sampling rates may also be used in various embodiments orsituations. The corresponding base time unit corresponding to one sampleat a given sampling rate is Ts=1/Fs seconds.

In some embodiments, a range of different FFT/IFFT sizes and cyclicprefix lengths are supported in order to address a wide variety ofpropagation conditions and different end user scenarios. A separateentity such as a scheduler may select appropriate FFT/IFFT size(s) andcyclic prefix length(s) for each frame based on the followingconsiderations.

First, determine the minimum subcarrier spacing needed to support theintended user mobility. Higher mobile velocities generally result inlarger Doppler shifts, which necessitate wider subcarrier spacing infrequency, Δf. The subcarrier spacing may be calculated as follows.Thus, larger FFT sizes are better adapted for decoding for fixedreceiving devices and smaller FFT sizes are better adapted for decodingfor mobile receiving devices, in various embodiments.

${\Delta \; f} = \frac{F_{S}}{{FFT}\mspace{14mu} {size}}$

As shown in the illustrated embodiment of FIG. 1B, each OFDM symbol witha total time length of T_(Sym) consists of two parts, a cyclic prefixwith a time length of T_(CP), and a useful portion with a time length ofT_(U). The useful portion 104 of the OFDM symbol 102 refers to theamount of data corresponding to the IFFT/FFT operations. The cyclicprefix 106 is a copy of the last N_(CP) samples 108 of the usefulportion of the OFDM symbol, and thus essentially represents overheadwhich is included in the OFDM symbol 102.

The useful portion of an OFDM symbol has a number of time samples equalto the size of the FFT (N_(FFT)), and a time length equal to:

$T_{U} = {{{FFT}\mspace{14mu} {size} \times T_{S}} = \frac{1}{\Delta \; f}}$

The cyclic prefix contains a specified number of samples (N_(CP)) with acorresponding time length of T_(CP). The cyclic prefix consists ofsample values copied from the useful portion (e.g., from the end) of thesame OFDM symbol and provides protection against inter-symbolinterference between successive OFDM symbols.

The number of subcarriers actually used within an FFT/IFFT may depend onboth the subcarrier spacing (a function of the FFT size and the samplingfrequency) and the bandwidth of the system, since the bandwidth occupiedby the used subcarriers should be less than the system bandwidth (e.g.,in order to allow for a guard band between adjacent channels). Note alsothat the direct current (DC) carrier is typically not used.

Table 1 shows a list of exemplary FFT sizes. FFT sizes that are aninteger power of 2 may be preferred in a wireless implementation forsimplification reasons, although non-power-of-2 sizes may be used insome embodiments. The time length (T_(U)) corresponding to the usableportion of each OFDM symbol, the subcarrier spacing (Δf), and themaximum Doppler velocity that can typically be handled at an examplecarrier frequency of 700 MHz are also shown. Here, the maximum Dopplervelocity is defined as the receiver velocity which results in a Dopplerfrequency shift equal to 10% of the subcarrier spacing. (It should beunderstood that the 10% used here is not essential to the presentlydisclosed inventions. Indeed, the percentage may take any value in arange of values.) The values in this table are based on the assumedexample sampling frequency of 12.288 MHz. Thus, signals adapted fordecoding by mobile devices at up to a particular maximum velocity mayactually be decodable at higher velocities, in some situations,depending on wireless propagation conditions, etc.

TABLE 1 Example FFT sizes, useful portion time lengths, subcarrierspacings, and maximum Doppler velocities for an example sampling rate of12.288 MHz: Maximum Doppler velocity FFT Size at 700 MHz (N_(FFT)) T_(U)(μs) Δf (Hz) (km/h) 1024 83 12000 1851 2048 167 6000 926 4096 333 3000463 8192 667 1500 231 16384 1333 750 116 32768 2667 375 58 65536 5333188 29

Table 2 shows similar information for a different example sampling rateof 18.432 MHz. As can be seen, for a given FFT size, a sampling rate of18.432 MHz results in a shorter OFDM symbol length (T_(U)), a widersubcarrier spacing (Δf), and a higher maximum Doppler velocity which canbe handled, as compared to a sampling rate of 12.288 MHz.

TABLE 2 Example FFT sizes, useful portion time lengths, subcarrierspacings, and maximum Doppler velocities for an example sampling rate of18.432 MHz FFT Size Maximum Doppler velocity (N_(FFT)) T_(U) (μs) Δf(Hz) at 700 MHz (km/h) 1024 56 18000 2777 2048 111 9000 1389 4096 2224500 694 8192 444 2250 347 16384 889 1125 174 32768 1778 563 87 655363556 281 43

Cyclic Prefix Lengths and Cyclic Prefix Length Selection

The cyclic prefix (CP) length for a given partition may be selected tomeet an intended range requirement. The cyclic prefix is typically usedto address inter-symbol interference between successive OFDM symbols.Such inter-symbol interference may arise from copies of the transmittedsignal with slightly different time delays arriving at the receiver,with such copies resulting from identical signal transmissions frommultiple base stations in a Single Frequency Network (SFN) and/orreflections of a transmitted signal in a multi-path propagationenvironment. Consequently, in an SFN with significant distances betweenneighboring base stations (or, potentially, in a propagation environmentwith significant multi-path scatter), a larger CP length would beselected. Conversely, in an SFN where neighboring base stations arecloser together, a shorter CP length may be used.

The CP length may be viewed as a percentage of the overall OFDM symbollength (giving the percent overhead consumed by the CP). However, forrange planning, it may be more useful to view the CP length as measuredin samples (as defined by the sampling frequency). For example, radiosignals will propagate approximately 24.4 meters in the time of onesample for the example sampling frequency of 12.288 MHz.

Table 3 (shown in FIG. 1C) gives cyclic prefix lengths (in number ofsamples) and corresponding ranges (in km) for various example cyclicprefix lengths specified relative to (as a percentage of) the usefulportion of each OFDM symbol. Again, the values in the table are based onthe example sampling frequency of 12.288 MHz.

The above cyclic prefix lengths should be considered to be illustrativeexamples only. In particular, cyclic prefix lengths should notnecessarily be considered to be restricted to be a power of two (or evena multiple of a power of two). Cyclic prefix lengths may have anypositive integer value.

Payload Data Terminology

In a wireless system, data may generally be transmitted in a series offrames, which correspond to a certain period of time. FIG. 2 shows ageneral overview of an exemplary frame structure. The frame 202 includesa payload region 204 which carries actual payload data and zero or morenon-payload regions 206 and 208 which may carry control information orother signaling information. In the example of FIG. 2, separatenon-payload regions 206 and 208 are shown by the shaded areas at thebeginning and end of the frame 202. The relative lengths in time(horizontal axis) and numbers of symbols for each region may or may notbe shown to scale in this example diagram.

The payload section of the frame may be referred to as the PhysicalFrame Data CHannel (PFDCH) and carries the actual payload data (asopposed to control or other signaling data) being transmitted by a basestation. In the illustrated embodiment, each frame has a time length of1 second. In some embodiments, the payload region (PFDCH) has a timelength of 990 ms. In other embodiments, however, payload regions andframes may have any of various appropriate time lengths.

An OFDM wireless frame (at least the payload portion of it, the PFDCH)is divided into OFDM symbols in the time dimension and sub-carriers inthe frequency dimension. The most basic (time-frequency) unit of datacarrying capability in OFDM is a resource element, which is defined asone sub-carrier in the frequency dimension by one OFDM symbol in thetime dimension. Each resource element may carry one QAM modulationsymbol (or QAM constellation).

The number of sub-carriers available for a fixed system bandwidth maydepend on the subcarrier spacing, which is in turn dependent upon theselected FFT size and sampling frequency. The time length of an OFDMsymbol may be dependent upon the selected FFT size and also upon theselected cyclic prefix length and sampling frequency. The number of OFDMsymbols available within a fixed period of time (such as the length of aframe) may be dependent upon the time lengths of the individual OFDMsymbols contained within that period of time.

The PFDCH may be divided into one or multiple partitions or PPDCHs(Physical Partition Data CHannel). A PPDCH is a rectangular logical areameasuring some number of sub-carriers in the frequency dimension andsome number of OFDM symbols within the time dimension. A PPDCH need notspan the full frequency bandwidth of the system, or the full time lengthof the PFDCH. This allows multiple PPDCHs to be multiplexed in timeand/or frequency within the same PFDCH, in some embodiments.

Different PPDCHs may have, but are not constrained to have, differentFFT sizes and/or different cyclic prefix lengths. Dividing a PFDCH intomultiple PPDCHs may support the provision of services to differentcategories of receiving devices. For example, fixed devices may beserved program data via a PPDCH with a large FFT size and closersubcarrier spacing, while mobile devices may be served program data viaa different PPDCH with a smaller FFT size and wider subcarrier spacing.

FIG. 3 shows two examples of partitioned PFDCHs 302 and 310. Theseexample configurations use the previously stated example frame length of1 second and PFDCH length of 990 ms, which leave a 10 ms non-payloadregion at the beginning of each example frame. In the first example, twoPPDCHs 304 and 306 use different FFT sizes and may be adapted to servenomadic and fixed users, respectively. In the second example, threePPDCHs 312, 314 and 316 use different FFT sizes and may be adapted toserve mobile, nomadic, and fixed users, respectively. The same cyclicprefix length as measured in samples may be used for all of the PPDCHsif the desired transmit ranges for different categories of users aredesired to be the same. However, there is no constraint requiring thesame cyclic prefix length to be used across multiple PPDCHs, so theconfigured cyclic prefix length may vary from one PPDCH to another, andthe use of different cyclic prefix lengths for different PPDCHs may infact be desirable for certain wireless provisioning scenarios.

For example, in some embodiments, different partitions in a payload areused to carry different types of content. In some embodiments, apartition with local content is configured with a smaller prefix sizethan a partition with regional content. This may allow the regionalcontent to be decodable by receiving devices in a greater area, whilerestricting the local content to nearby devices. In some embodiments,different base stations may be configured to transmit local content andregional content. For example, multiple local base stations may cover asimilar area to a single regional base station. In these embodiments,the base stations may be configured to blank transmissions during one ormore pre-arranged partitions. For example, for a partition used by thelocal base stations to transmit local content, the regional base stationmay refrain from transmitting using time and/or frequency resourcesassigned to that partition. Similarly for a partition used by theregional base station to transmit regional content, the local basestations may refrain from transmitting using time and/or frequencyresources assigned to that partition.

Although the PPDCHs in FIG. 3 are the same size, there is no requirementfor PPDCHs within the same frame to be of the same length. Indeed, sincedifferent modulation levels and code rates may often be used withindifferent PPDCHs, the data carrying capacities of different PPDCHs mayalso be very different. FIG. 4 shows a frame whose PFDCH 320 includes: afirst partition 322 of length 660 ms and 8K FFT size; and a secondpartition 326 of length 330 ms and 64K FFT size.

Each PPDCH within a frame may contain zero or more Physical Service DataCHannels (PSDCH). (Note also that part or all of the physical resourceswithin a PPDCH may be left unused.) The contents of a PSDCH are encodedand transmitted using a specified set of physical resources within thecorresponding PPDCH, in some embodiments. Each PSDCH corresponds to onetransport block for data carrying purposes, in some embodiments. Atransport block may correspond to a Medium Access Control (MAC) ProtocolData Unit (PDU) and represent a set of data bytes from upper layers tobe transmitted.

The relationship between the various payload-related physical channels,according to some embodiments, is illustrated in FIG. 5. In theillustrated embodiment, each frame contains one Physical Frame DataCHannel (PFDCH) 502. The PFDCH 502 contains one or more PhysicalPartition Data CHannels (PPDCH) 504. Each PPDCH 504 contains zero ormore Physical Service Data CHannels (PSDCH) 506.

There is no general constraint that a PPDCH include more than one PSDCH.FIG. 6 illustrates the case where two PPDCHs each include only onePSDCH. In particular, PPDCH 604A and PPDCH 604B in PFDCH 602 eachinclude only one PSDCH, and PPDCH 604C includes a plurality of PSDCHs.(The PSDCHs in FIG. 6 are each labelled 606.) Furthermore, it ispossible that the PFDCH may include only a single PPDCH, e.g., as shownin FIG. 7. In particular, PFDCH 612 includes the single PPDCH 614. PPDCH614 includes one or more PSDCHs, each labeled 616.

Payload Structure and Mapping

This section provides detailed examples as to how the PFDCH of awireless frame is structured, how payload partitions (PPDCHs, PhysicalPartition Data CHannels) are specified, how PSDCHs are mapped tospecific physical resources, etc., in some embodiments. As such, thecontents of this section may build on the concepts that were introducedearlier.

In some embodiments, the concept of mapping virtual resources to logicalresources and then logical resources to physical resources is used togenerate a payload.

Payload Partition Mapping

In a physical sense, the PFDCH consists of a number of consecutivesamples in the time domain. This number of samples is equal to the totalnumber of samples in one frame (e.g. 12.288 million samples for theexample sampling frequency of 12.288 MHz and example frame length of 1second) minus the lengths (in samples) of any non-payload regions in theframe.

In a logical sense, the PFDCH is composed of a number of OFDM symbols inthe time domain and a number of subcarriers in the frequency domain. Thesum of the lengths in samples of all OFDM symbols within the PFDCHshould be less than or equal to the number of samples available for thePFDCH as calculated above.

In some embodiments, OFDM symbols belonging to the same PPDCH will havethe same lengths, but OFDM symbols belonging to different PPDCHs mayhave different lengths. Consequently, not all OFDM symbols within thePFDCH will necessarily have the same length, in various embodiments.

Similarly, the number of subcarriers in the frequency domain is afunction of the system bandwidth and the subcarrier spacing. Thesubcarrier spacing is dependent upon the selected FFT size and thesampling frequency, and may thus vary from one PPDCH to another, ifdistinct FFT sizes are configured for the two PPDCHs.

In various embodiments, different PPDCHs may be multiplexed in timeand/or frequency. Thus, two given PPDCHs may share the same time slotand be frequency multiplexed, two given PPDCHs may share the samefrequency resources and be time multiplexed, or both situations mayoccur for a given frame.

Each PPDCH may be referenced via an index (e.g. PPDCH #0, PPDCH #1, . .. ), which may facilitate assigning PSDCHs to specific PPDCHs.

The physical resources allocated to a PPDCH may be specified via thefollowing sets of characteristics.

-   -   (1) FFT size and cyclic prefix length (these characteristics        determine the length of each OFDM symbol within the PPDCH, in        some embodiments)    -   (2) Physical resources allocated to the PPDCH in the time        dimension.    -   (3) Physical resources allocated to the PPDCH in the frequency        dimension.

Specifying PPDCH Physical Resources in the Time Dimension

In the time dimension, a specific PPDCH may be defined using thefollowing quantities:

-   -   (a) Total number of OFDM symbols assigned to this PPDCH;    -   (b) Absolute OFDM symbol starting position within the PFDCH for        this PPDCH (indexing begins at 0, for the examples discussed        herein);

As an illustrative example, consider the payload partitioning shown inFIG. 3 with corresponding example parameter settings shown in Table 4,where there are three equally-sized (in the time dimension) PPDCHs. As aresult, the PFDCH contains a total of 440+232+60=732 OFDM symbols inthis example.

-   -   PPDCH #0 contains OFDM symbols 0 through 439, each of length        9216 samples.    -   PPDCH #1 contains OFDM symbols 440 through 671, each of length        17408 samples.    -   PPDCH #2 contains OFDM symbols 672 through 731, each of length        66560 samples.

TABLE 4 Exemplary PPDCH parameters (time dimension) for FIG. 3 QuantityPPDCH #0 PPDCH #1 PPDCH #2 PPDCH length (seconds) 0.330 s 0.330 s 0.330s PPDCH length (samples) 4,055,040 4,055,040 4,055,040 FFT size 819216384 65536 CP length (samples) 1024 1024 1024 OFDM symbol length 921617408 66560 (samples) Total number of OFDM 440 232 60 symbols AbsoluteOFDM symbol 0 440 672 starting position

Specifying PPDCH Physical Resources in the Frequency Dimension

The subcarriers within each OFDM symbol may be divided into useful andnon-useful subcarriers. Useful subcarriers lie within the systembandwidth minus a guard band, with the exception of the DC subcarrierwhich is considered a non-useful subcarrier. Non-useful subcarriers lieoutside the system bandwidth minus the guard band.

The number of useful subcarriers may be a function of the FFT size andsampling frequency (which together determine the subcarrier spacing) andthe system bandwidth.

Refer to FIG. 8 for additional details relating to useful and non-usefulsubcarriers, according to some embodiments. Within the full IFFT/FFTrange (size) 702, the useful subcarriers 704 are those which lie withinthe system bandwidth 706 minus a guard band, with the exception of theDC subcarrier 708. Non-useful subcarriers 710 lie outside the systembandwidth minus the guard band.

There is no requirement that all useful subcarriers (resource elements)in an OFDM symbol be explicitly assigned to a PPDCH. Note that eachuseful resource element is assigned to a maximum of one PPDCH, in someembodiments. Any useful resource elements that are not associated with aPPDCH may be assigned a value of 0. Non-useful subcarriers (resourceelements) may also be assigned a value of 0.

In the frequency dimension, a specific PPDCH may be defined via thefollowing quantities: the number of useful subcarriers belonging to thePPDCH and the absolute index of the first subcarrier belonging to thePPDCH. The number of useful subcarriers is less than or equal to thetotal number of all useful subcarriers per OFDM symbol. This specifiesthe actual size of the PPDCH in the frequency dimension. The DCsubcarrier is not considered to be a useful subcarrier, so if the DCsubcarrier happens to lie within a particular PPDCH, then thatsubcarrier is not counted against the number of useful subcarriersbelonging to that PPDCH, in some embodiments. Subcarriers may be indexedbeginning at 0 and proceeding sequentially upwards to the total numberof subcarriers minus 1 (e.g., the FFT size minus 1). Subcarrier 0 istherefore essentially the lowest frequency subcarrier.

Multiple PPDCHs may be multiplexed beside each other in the frequencydimension. In some embodiments, however, there is no actual interleavingof PPDCHs in the frequency dimension. In other embodiments, PPDCHs maybe interleaved in the time and/or frequency dimension and thus may ormay not be contiguous in either dimension. That is, in the frequencydimension, each PPDCH occupies a contiguous set of physical subcarriers.

FIG. 9 shows an example of two PPDCHs 802 and 804 that have beenmultiplexed beside each other in the frequency dimension. Approximately⅔ of the useful subcarriers have been allocated to PPDCH #0 (802), withthe remaining ⅓ of the useful subcarriers being allocated to PPDCH #1(804). Table 5 contains the corresponding PPDCH parameters in thefrequency dimensions for the two example PPDCHs 802 and 804 shown inFIG. 9. In this example, both PPDCHs have been configured to use thesame FFT size and cyclic prefix length.

TABLE 5 Example PPDCH parameters (frequency dimension) for FIG. 9Quantity PPDCH #0 PPDCH #1 FFT size 16384 16384 CP length (samples) 10241024 Subcarrier spacing 750 Hz 750 Hz System bandwidth 6 MHz 6 MHz Totalnumber of all useful 7600 7600 subcarriers Number of useful subcarriers5000 2600 assigned to this PPDCH Index of the first subcarrier 4392 9393belonging to this PPDCHPSDCH Mapping within a PPDCH

In some embodiments, PSDCHs are mapped to virtual resources within theirassigned PPDCH, virtual resources are then mapped to logical resourceswithin the same PPDCH, and then the logical resources of each PPDCH aremapped to actual physical resources within the PFDCH. This process isdescribed in detail in the following sections.

Logical Resources for a PPDCH

It has previously been described how a particular PPDCH is associatedwith corresponding physical resources. Regardless of the physicalresources belonging to a PPDCH, the logical resources of a PPDCH may beconsidered to be contiguous in both the frequency and time dimensions,in some embodiments, as illustrated in FIG. 10. Here, the logicalsubcarriers 904 of a PPDCH 902 begin numbering at 0 at the left side ofthe diagram (lowest frequency) and progress sequentially upwards to theright. Similarly, the logical OFDM symbols 906 of the PPDCH 902 beginnumbering at 0 at the top of the diagram (earliest time) and progresssequentially upwards moving forward through time (toward the bottom ofthe diagram).

FIG. 11 introduces additional logical resource concepts for the contentsof a PPDCH. A stripe refers to a set of resources measuring onesubcarrier in the frequency dimension and running for the full timeduration of the PPDCH (i.e. all of the OFDM symbols) in the timedimension. Stripes may be grouped together in the frequency dimensioninto subbands, where the subband width of each subband in the frequencydimension is equal to the number of stripes specified for the PPDCH.Each logical subband is composed of a number of logical stripes asillustrated in the diagram, which shows four logical subbands 1004,1006, 1008 and 1010, each composed of ten logical stripes. A particularstripe 1002 within the PPDCH's logical resources may be referenced viathe logical subband index 1006 and the logical stripe index 1002 withinthat logical subband 1006. As shown in the diagram, logical subcarriersmay begin with the lowest frequency subcarrier at the left and progressupwards in frequency while moving towards the right. Logical subbandsmay be indexed beginning with 0 and progress sequentially upwards withfrequency.

In some embodiments, the number of useful subcarriers assigned to aPPDCH is an integer multiple of the subband-width for that same PPDCH,so that each PPDCH will always contain an integer number of subbands.However, there is no requirement that PPDCH assignments begin withsubband 0 or end with subband N−1. In fact, the system may electivelydepopulate subbands at the band edges to facilitate spectrum sharing orotherwise constrain out-of-band emissions relative to a prescribedspectral mask.

Virtual Resources for a PPDCH

Corresponding to each logical subband (containing a number of logicalstripes) is an equally-sized virtual subband containing the same numberof virtual stripes, in some embodiments. Within each subband, thereexists a one-to-one mapping of virtual stripes to logical stripes on aper OFDM symbol basis. This may be considered to be conceptuallyequivalent to shuffling the virtual stripes in order to obtain thelogical stripes. A virtual subband has the same index as thecorresponding logical subband, in some embodiments.

FIG. 12 illustrates this concept with an example. In the illustratedexample, each subband has a width of ten stripes (W_(SB)=10). The tenvirtual stripes 1106 belonging to the virtual subband 1102 at the tophave a one-to-one stripe mapping 1108 to the ten logical stripes 1110belonging to the logical subband 1104 at the bottom. The stripe mapping1108 is dependent on the current logical OFDM symbol index 1112, and maytherefore vary from one logical OFDM symbol to the next.

Table 6 contains an example virtual-to-logical stripe mapping whileTable 7 contains a corresponding example logical-to-virtual stripemapping. Note that the stripe mapping may vary as a function of thelogical OFDM symbol index and has a periodicity of P_(SM)=10 in the timedimension in this example. Without loss of generality, it may be assumedthat virtual stripe #0 is reserved for a reference symbol or pilotsymbol, in some embodiments. In Table 7, the logical stripes thatcontain reference symbols (i.e. which map to virtual stripe #0) havebeen highlighted with boldface text to show the reference symbol patternbeing used in this example. In this example, the reference symbolpattern repeats every five logical OFDM symbols, while the data stripemapping pattern repeats every ten logical OFDM symbols.

In Table 6, the logical OFDM symbol index (row index) and the virtualstripe index (column index) may be used to determine the table entrythat corresponds to the logical stripe index for that particular pair oflogical OFDM symbol and virtual stripe indices. Conversely, in Table 7,the logical OFDM symbol index (row index) and the logical stripe index(column index) may be used to determine the table entry that correspondsto the virtual stripe index for that particular pair of logical OFDMsymbol and logical stripe indices.

TABLE 6 Example virtual stripe to logical stripe mapping Logical OFDMsymbol index Virtual stripe index mod 10 0 1 2 3 4 5 6 7 8 9 0 0 2 3 4 56 7 8 9 1 1 4 8 9 0 1 2 3 5 6 7 2 8 4 5 6 7 9 0 1 2 3 3 2 0 1 3 4 5 6 78 9 4 6 7 8 9 0 1 2 3 4 5 5 0 3 4 5 6 7 8 9 1 2 6 4 9 0 1 2 3 5 6 7 8 78 5 6 7 9 0 1 2 3 4 8 2 1 3 4 5 6 7 8 9 0 9 6 8 9 0 1 2 3 4 5 7

TABLE 7 Example logical stripe to virtual stripe mapping Logical OFDMsymbol Logical stripe index index mod 10 0 1 2 3 4 5 6 7 8 9 0 0 9 1 2 34 5 6 7 8 1 3 4 5 6 0 7 8 9 1 2 2 6 7 8 9 1 2 3 4 0 5 3 1 2 0 3 4 5 6 78 9 4 4 5 6 7 8 9 0 1 2 3 5 0 8 9 1 2 3 4 5 6 7 6 2 3 4 5 0 6 7 8 9 1 75 6 7 8 9 1 2 3 0 4 8 9 1 0 2 3 4 5 6 7 8 9 3 4 5 6 7 8 0 9 1 2

As part of the set of parameters for each PPDCH, the followingquantities may therefore be indicated.

-   -   (A) Subband width in the frequency dimension (in units of        stripes (or subcarriers)).    -   (B) Stripe mapping periodicity in the time dimension (in units        of logical OFDM symbols). Note that the number of logical OFDM        symbols in a PPDCH is not required to be an integer multiple of        the stripe mapping periodicity.    -   (C) Stripe mapping, which may be in the form of a table with the        number of columns equal to the subband width and the number of        rows equal to the stripe mapping periodicity. Alternatively, a        more compact form of signaling the stripe mapping such as        described in the following section may be used, in some        embodiments.

In some embodiments, the concept of virtual OFDM symbols is not definedbecause virtual OFDM symbols are essentially directly equivalent tological OFDM symbols (i.e. virtual OFDM symbol #N is the same as logicalOFDM symbol #N).

Compact Signaling of Logical-to-Virtual Stripe Mapping

Signaling a complete logical-to-virtual stripe mapping over the air mayresult in an inefficient use of limited wireless resources due to thepotential size of the stripe mapping table that should be transmittedfor each PPDCH.

This section describes a more compact form of signaling the stripemapping to be used at the receiver, in some embodiments. This compactsignaling may allow the full logical to virtual stripe mapping table tobe constructed at the receiver for each PPDCH.

Two desirable characteristics for a good virtual to logical stripemapping (and vice versa) are as follows: (1) the stripe mapping shouldsupport the ability to have scattered reference symbols (e.g., theability to map reference symbols to different logical stripes indifferent logical OFDM symbols) and (2) the stripe mapping should varythe virtual data stripes that are mapped to the logical stripes adjacentto the reference symbol to avoid some virtual data stripes consistentlyhaving better channel estimates than other virtual data stripes.

A stripe mapping algorithm for each PPDCH may include the followinginformation, which may reduce the amount of information needing to besignaled over the air. Stripe mapping periodicity (P_(SM)) may be thesame quantity as has previously been defined. A vector of referencesymbol logical stripe mapping positions (L_(RS)(k)) with length equal tothe stripe mapping periodicity may be determined. For each OFDM symbol k(modulo P_(SM)), this may specify the logical stripe to which virtualstripe 0 (which contains reference symbols) maps. This may allow thereference symbol position to be varied on an OFDM symbol by symbolbasis. A vector of stripe rotation values with length equal to thestripe mapping periodicity may also be determined. For each OFDM symbolk (modulo P_(SM)), this may specify the “rotation” to be applied toeither:

(1) the virtual stripes other than virtual stripe 0 (i.e. all of thevirtual stripes that carry data rather than a reference symbol) in orderto obtain logical stripe indices (this quantity may be labelledR_(VL)(k)) or (2) the logical stripes other than the logical stripeL_(RS)(k) which carries the reference symbol (i.e. all of the logicalstripes that carry data rather than a reference symbol) in order toobtain virtual stripe indices (this quantity may be labelled R_(LV)(k)).

Table 8 contains the compact form for specifying the stripe mapping forthe example corresponding to Table 6 and Table 7, according to someembodiments. Recall that for this example, the stripe mappingperiodicity is P_(SM)=10, and the width of the subband is W_(SB)=10. Inaddition, the relation between the virtual to logical and logical tovirtual stripe rotations is simply

R _(VL)(k)+R _(LV)(k)=W _(SB)−1.

TABLE 8 Example compact form for signaling of stripe mapping dataLogical Virtual to logical OFDM symbol Logical stripe for striperotation for Logical to virtual index mod reference symbol data striperotation 10 (k) (L_(RS)(k)) (R_(VL)(k)) for data (R_(LV)(k)) 0 0 1 8 1 47 2 2 8 3 6 3 2 9 0 4 6 6 3 5 0 2 7 6 4 8 1 7 8 4 5 8 2 0 9 9 6 7 2

FIG. 13 illustrates a conceptual view of how the virtual to logicalstripe rotation works, in some embodiments. This example corresponds tomodulo logical OFDM symbol k=6 from Table 8. As can be seen, thereference symbol on virtual stripe 0 (1202) is mapped straight throughto logical stripe L_(RS)(k)=4 (1204). A rotation (modulo W_(SB)=10) ofR_(VL)(k)=8 is applied to the data virtual stripes 1206, and then theserotated data virtual stripes 1208 are mapped essentially straightthrough to the available logical stripes 1210 (i.e. all of the logicalstripes with the exception of logical stripe #4 (1204) which is alreadyoccupied by the reference symbol).

FIG. 14 shows the corresponding logical to virtual stripe rotation andmapping for modulo logical OFDM symbol k=6 from Table 8. Here, thelogical stripe carrying the reference symbol (L_(RS)(k)=4 (1302)) isextracted and mapped onto virtual stripe #0 (1304). A rotation (moduloW_(SB)=10) of R_(LV)(k)=1 is applied to the data logical stripes 1308,and then these rotated data logical stripes 1310 are mapped straightthrough onto the data virtual stripes 1312 (i.e. virtual stripes #1through #9).

Let k represent the logical OFDM symbol index modulo the stripe mappingperiodicity (P_(SM)=10, in this example). At the transmitter, areference symbol for modulo symbol k is mapped from virtual stripe index0 to the corresponding logical stripe index L_(RS)(k)(0≤L_(RS)(k)<W_(SB)) given in the table.

S _(L)(k,L _(RS)(k))=S _(V)(k,0)

At the receiver, this process is reversed, and a reference symbol formodulo symbol k is mapped from the corresponding logical stripe indexL_(RS)(k) given in the table back to virtual stripe index 0.

S _(V)(k,0)=S _(L)(k,L _(RS)(k))

For virtual to logical data stripe mapping at the transmitter, thefollowing procedure may be followed. Let S_(V)(k,i)(0<S_(V)(k,i)<W_(SB)) and S_(L)(k,i) (0≤S_(L)(k,i)<W_(SB) andS_(L)(k,i)≠L_(RS)(k)) represent a corresponding pair of virtual andlogical stripe indices that map to each other for modulo symbol k(0≤k≤P_(SM)). Let R_(VL)(k) (0≤R_(VL)(k)<W_(SB) andR_(VL)(k)≠(L_(RS)(k)+W_(SB)−1) mod W_(SB)) represent the virtual tological stripe rotation for data for modulo symbol k. The logical datastripe index S_(L) (k,i) corresponding to a particular virtual datastripe index S_(V)(k,i) (0<i<W_(SB)) may then be calculated as follows,noting that for a valid stripe mapping R_(VL)(k)≠(L_(RS)(k)+W_(SB)−1)mod W_(SB) implies that R_(VL)(k)+1≠L_(RS)(k) for all k.

${\overset{\sim}{L}(k)} = \{ {{\begin{matrix}{L_{RS}(k)} & {{{{if}\mspace{14mu} {R_{VL}(k)}} + 1} < {L_{RS}(k)}} \\{{L_{RS}(k)} + W_{SB}} & {{{{if}\mspace{14mu} {R_{VL}(k)}} + 1} > {L_{RS}(k)}}\end{matrix}i} = {{{1\mspace{14mu} \ldots \mspace{14mu} W_{SB}} - {1{S_{V}( {k,i} )}}} = {{i{\overset{\sim}{S}( {k,i} )}} = {{{S_{V}( {k,i} )} + {{R_{VL}(k)}{S_{L}( {k,i} )}}} = \{ \begin{matrix}{{\overset{\sim}{S}( {k,i} )}\mspace{11mu} {mod}\mspace{11mu} W_{SB}} & {{{if}\mspace{14mu} {\overset{\sim}{S}( {k,i} )}} < {\overset{\sim}{L}(k)}} \\{( {{\overset{\sim}{S}( {k,i} )} + 1} )\mspace{11mu} {mod}\mspace{11mu} W_{SB}} & {{{if}\mspace{14mu} {\overset{\sim}{S}( {k,i} )}} \geq {\overset{\sim}{L}(k)}}\end{matrix} }}}} $

At the receiver, the virtual data stripe index S_(V)(k,i) correspondingto a particular logical data stripe index S_(L)(k,i) (0≤i<W_(SB) andi≠L_(RS)(k)) may then be calculated as shown below.R_(LV)(k)=W_(SB)−R_(VL)(k)−1 represents the virtual to logical striperotation for data for modulo symbol k.

  x(k) = W_(SB) − R_(LV)(k)  i = 0  …  W_(SB) − 1  and  i = L_(RS)(k)   S_(L)(k, i) = i${{{If}\mspace{14mu} {x(k)}} < {{L_{RS}(k)}\text{:}\mspace{14mu} {S_{V}( {k,i} )}}} = \{ {{\begin{matrix}{( {{S_{L}( {k,i} )} + {R_{LV}(k)}} )\mspace{11mu} {mod}\mspace{11mu} W_{SB}} & \begin{matrix}{{{if}\mspace{14mu} {S_{L}( {k,i} )}} < {{x(k)}\mspace{14mu} {or}}} \\{{S_{L}( {k,i} )} > {L_{RS}(k)}}\end{matrix} \\{( {{S_{L}( {k,i} )} + {R_{LV}(k)} + 1} )\mspace{11mu} {mod}\mspace{11mu} W_{SB}} & {{{if}\mspace{14mu} {x(k)}} \leq {S_{L}( {k,i} )} < {L_{RS}(k)}}\end{matrix}{Conversely}},{{{{if}\mspace{14mu} {x(k)}} \geq {{L_{RS}(k)}\text{:}\mspace{14mu} {S_{V}( {k,i} )}}} = \{ \begin{matrix}{( {{S_{L}( {k,i} )} + {R_{LV}(k)}} )\mspace{11mu} {mod}\mspace{11mu} W_{SB}} & {{{if}\mspace{14mu} {L_{RS}(k)}} < {S_{L}( {k,i} )} < {x(k)}} \\{( {{S_{L}( {k,i} )} + {R_{LV}(k)} + 1} )\mspace{11mu} {mod}\mspace{11mu} W_{SB}} & \begin{matrix}{{{if}\mspace{14mu} {S_{L}( {k,i} )}} < {{L_{RS}(k)}\mspace{14mu} {or}}} \\{{S_{L}( {k,i} )} \geq {x(k)}}\end{matrix}\end{matrix} }} $

Table 9 summarizes the list of parameters to be provided for each PPDCHwithin the PFDCH, in some embodiments.

TABLE 9 Summary of parameters for each PPDCH Parameter CategoryParameter General PPDCH index (may be implicitly signaled by positionwithin a list of PPDCHs) FFT size Cyclic prefix length (in samples) TimeTotal number of OFDM symbols assigned to this PPDCH dimension AbsoluteOFDM symbol starting position within the PFDCH for this PPDCH FrequencyNumber of useful subcarriers assigned to this PPDCH dimension (should bean integer multiple of the subband width further below) Absolute indexof the first subcarrier belonging to this PPDCH Stripe Subband width inthe frequency dimension (in units of mapping stripes or subcarriers)Stripe mapping periodicity in the time dimension (in units of logicalOFDM symbols) Virtual↔Logical stripe mapping table or compact stripemapping signaling format

Mapping a PSDCH to Virtual Resources

Virtual stripe #0 may always be reserved for reference symbols, in someembodiments. This does not result in any loss of generality sincevirtual stripe #0 may be mapped to any desired logical stripe.

The reference symbol density may be calculated as the reciprocal of thesubband width. In the examples given above with a subband width of 10,the reference symbol density is 10%. Conversely, any of various desiredreference symbol densities may be used to obtain the appropriate subbandwidth to configure.

A subband block is defined as a set of resource elements measuring onesubband in the frequency dimension by one OFDM symbol in the timedimension. Resources may be allocated to a PSDCH in units of subbandblocks, where a subset of the virtual stripes within each virtualsubband may be assigned to a particular PSDCH.

Virtual resources may be assigned to a PSDCH via the followingparameters, in some embodiments:

-   -   Total number of subband blocks allocated to this PSDCH.    -   Subband index of the first subband block allocated to this        PSDCH.    -   Number of consecutive subband blocks per subband cluster period        allocated to this PSDCH (Subband cluster size). The first        subband for a logical OFDM symbol is considered to be        consecutive to the last subband for the preceding logical OFDM        symbol.    -   Subband cluster periodicity for this PSDCH. This specifies the        periodicity of successive subband clusters that are allocated to        this PSDCH.    -   Index of the first allocated virtual stripe within a virtual        subband for this PSDCH.    -   Number of consecutive allocated virtual stripes within a virtual        subband for this PSDCH. (Stripe cluster size)    -   Index of the first logical OFDM symbol occupied by this PSDCH.    -   Number of consecutive logical OFDM symbols per logical OFDM        symbol cluster occupied by this PSDCH. (Logical OFDM symbol        cluster size)    -   Logical OFDM symbol cluster periodicity for this PSDCH.

Note that the total number of resource elements allocated to a PSDCH maybe obtained by multiplying the total number of allocated subband blocksby the number of consecutive allocated virtual stripes within a virtualsubband.

FIG. 15 illustrates how the above parameters may be used to map a PSDCHonto a set of virtual resources within a PPDCH. Table 10 contains theparameters that correspond to the example PSDCH mapping shown in FIG.15. In this example, the total number of resource elements allocated tothis PSDCH is equal to 16 (total number of allocated subband blocks)multiplied by 4 (number of consecutive allocated virtual stripes withina virtual subband), which equals 64. In the diagram, most but not all ofthe subband clusters have been circled to show which subbands belong towhich subband clusters.

TABLE 10 Example PSDCH virtual resource mapping parameters ParameterValue Total number of allocated subband blocks 16 Subband index of firstsubband block 1 Subband cluster size 2 Number of consecutive subbandblocks per subband cluster period Subband cluster periodicity 3 Index offirst allocated virtual stripe within a virtual subband 6 Stripe clustersize 4 Number of consecutive allocated virtual stripes within a virtualsubband Index of first occupied logical OFDM symbol 4 Logical OFDMsymbol cluster size 3 Number of consecutive logical OFDM symbols perOFDM symbol period Logical OFDM symbol cluster periodicity 8

Within a virtual resource mapping for a PSDCH, modulation symbols may bemapped to resource elements beginning with the first allocated virtualstripe of the first allocated subband block of the first occupiedlogical OFDM symbol, and progressing by virtual stripe within eachsubband block, then by subband block within the same logical OFDMsymbol, and finally by logical OFDM symbol.

In the above example, modulation symbols will be mapped to virtualstripes 6/7/8/9 of virtual subband 1 and logical OFDM symbol 4, then tovirtual stripes 6/7/8/9 of virtual subband 2 and logical OFDM symbol 4,then to virtual stripes 6/7/8/9 of virtual subband 0 and OFDM symbol 5,then to virtual stripes 6/7/8/9 of virtual subband 1 and OFDM symbol 5,and so on until the total number of allocated subband blocks has beenprocessed.

Frame Content Description Provided to the Receiver

Information about the payload content formatting of each frame,including information on the encoding, FFT sizes, etc, should beprovided to the receiver to facilitate the receiver processing anddecoding of the payload contents. There are a variety of methods thatmay be used to communicate this formatting information to the receiver.For example, the payload content descriptions could be signaled withineach frame in one of the non-payload regions shown in FIG. 2.Alternatively, if the payload content structure varies more slowly thanon a frame-by-frame basis, then the payload content descriptions couldbe signaled on an as-required basis.

In general, the receiver should be provided with descriptions of thefollowing items.

Number of distinct PPDCHs in the frame

For each PPDCH:

-   -   Physical resources allocated to that PPDCH. This may include the        number of OFDM symbols allocated to that PPDCH, as well as which        particular symbols are allocated to that PPDCH.    -   FFT size    -   Cyclic prefix length

Number of PSDCHs in the frame.

For each PSDCH

-   -   Service associated with that PSDCH. (The service may be thought        of as the data stream flow to which a particular PSDCH belongs.        For example, a specific television program may be considered to        be a particular service.)    -   Physical resources allocated to that PSDCH.    -   Modulation used for that PSDCH.    -   Transport block size (bytes).

Table 11, Table 12, and Table 13 provide more detailed descriptions ofthe parameter fields to be provided to the receiver. One PFDCHdescriptor (Table 11) may be provided for each frame. One PPDCHdescriptor (Table 12) may be provided for each PPDCH contained in theframe. One PSDCH descriptor (Table 13) may be provided for each PSDCHcontained in the frame.

TABLE 11 PFDCH descriptor Field description Number of PPDCHs

TABLE 12 PPDCH descriptor Field description FFT size (e.g. 2048, 4096,8192, 16384, 32768, 65536) Cyclic prefix length Total number of OFDMsymbols in this PPDCH Absolute OFDM symbol starting position for thisPPDCH Number of useful subcarriers for this PPDCH Absolute index of thefirst subcarrier belonging to this PPDCH Subband width (Note that thenumber of useful subcarriers belonging to the PPDCH should be an integermultiple of the subband width) Stripe mapping periodicity in the timedimension Logical-to-virtual stripe mapping table or Compact stripemapping parameters Number of PSDCHs in the PPDCH

TABLE 13 PSDCH descriptor Field description Service associated with thisPSDCH Transport block size FEC coding type (e.g. Turbo, Low DensityParity Check (LDPC)) Modulation level (e.g. QPSK, 16QAM, 64QAM, 256QAM)Total number of subband blocks for this PSDCH Subband index of the firstsubband block for this PSDCH Subband cluster size for this PSDCH Subbandcluster periodicity for this PSDCH Index of the first allocated virtualstripe within a virtual subband for this PSDCH Number of consecutiveallocated virtual stripes within a virtual subband for this PSDCH Indexof the first logical OFDM symbol occupied by this PSDCH Logical OFDMsymbol cluster size (Number of consecutive logical OFDM symbols per OFDMsymbol period occupied by this PSDCH) Logical OFDM symbol clusterperiodicity for this PSDCH

FIG. 16 shows an example of how the various descriptors may becommunicated to the receiver. In this example, the single PFDCHdescriptor 1502 per frame occurs first, immediately followed by all ofthe concatenated PPDCH descriptors 1504 (this example frame contains n+1PPDCHs), which in turn are followed by all of the concatenated PSDCHdescriptors 1506 (in this example frame, PPDCH #0 has p+1 PSDCHs andPPDCH #n has q+1 PSDCHs).

The ordering of the descriptors shown in FIG. 16 may be rearranged if sodesired. For example, the PSDCH descriptors associated with a particularPPDCH may follow immediately after the descriptor for that PPDCH,instead of all being concatenated together following the group ofconcatenated PPDCH descriptors.

In one set of embodiments, a method 1700 for constructing andtransmitting a frame may include the actions shown in FIG. 17. (Themethod 1700 may also include any subset of the features, elements andembodiments described above.) The method may be implemented by a basestation (or access point).

At 1710, digital circuitry of the base station may receive (e.g., from abroadcast gateway) or generate a payload region for a frame of wirelessdata. In the illustrated embodiment, the payload region includes aplurality of partitions that each include multiple orthogonalfrequency-division multiplexing (OFDM) symbols. In the illustratedembodiment, different ones of the partitions have different frequencytransform sizes for the OFDM symbols in the ones of the partitions.

At 1720, a transmitter of the base station may transmit the frame ofwireless data, including the payload region, over a wireless channel.

In some embodiments, the operations also include embedding partitioninformation (which may also be referred to as signaling information) ina non-payload region of the frame, e.g., as variously described above.The partition information may indicate the FFT size and/or the cyclicprefix size for each of the partitions. In other embodiments, thesignaling information may be embedded elsewhere, e.g., in a previousframe.

In some embodiments, different ones of the partitions have differentcyclic prefix sizes (e.g., different percentages of the OFDM symbols inthe different partitions may be used as a cyclic prefix). In someembodiments, the partitions may be used to convey different content,e.g., local v. regional programming.

In some embodiments, each of the partitions includes a corresponding setof overhead resource elements (such as reference symbols). In theseembodiments, the above-described operations may also include schedulingsymbol data from one or more service data streams to each of thepartitions after having reserved the overhead resource elements withinthe frame.

Different partitions may have different values of FFT size, and thus,different values of subcarrier spacing. (As discussed above, thesubcarrier spacing for any given partition is the ratio of sample rateto the FFT size for that partition.) Consequently, the differentpartitions will have different amounts of Doppler tolerance (i.e.,tolerance to Doppler shift due to motion of user devices). For example,a first of the partitions may be targeted for transmission to mobiledevices, while a second of the partitions is targeted for transmissionto fixed devices. Thus, the FFT size corresponding to the firstpartition is configured to be smaller than the FFT size corresponding tothe second partition. This allows the first partition to have largersubcarrier spacing, and thus, greater tolerance to the frequency shiftof subcarriers due to motion of the mobile devices.

Furthermore, different partitions may have different cyclic prefix sizes(or guard interval durations), and thus, be able to tolerate differentamounts of delay spread. For example, a first of the partitions may betargeted for transmission to a first set of user devices that areexpected to have large delay spreads, while a second of the partitionsis targeted for transmission to a second set of user devices that areexpected to have smaller delay spreads. Thus, the cyclic prefix size forthe first partition is configured to be larger than the cyclic prefixsize for the second partition, in some embodiments.

A given user device may receive the transmitted frame using a wirelessreceiver, and extract the OFDM symbols from the partition to which theuser device has been assigned. The OFDM symbols are decoded to obtaindigital information signals, which are then displayed or otherwiseoutputted to a user. (The base station may signal to each user device oreach type of user device the partition to which it is assigned. The basestation may also signal the type of service carried in each partition.)

Thus, in some embodiments, a mobile device may include a wireless radio,one or more antennas, and one or more processors. In some embodiments,the mobile device is configured to receive, using the wireless radio, aframe of wireless data that includes a plurality of partitions andpartition data. In some embodiments, the plurality of partitions eachinclude multiple orthogonal frequency-division multiplexing (OFDM)symbols, and different ones of the partitions have different frequencytransform sizes (e.g., different FFT sizes). In some embodiments, thepartition data indicates the frequency transform sizes for the ones ofthe partitions. In some embodiments, the mobile device is configured toselect, based on the partition data, one or more of the plurality ofpartitions and decode the selected one or more partitions to determinedata represented by the OFDM symbols in the selected one or morepartitions.

In some embodiments, the mobile device may select the one or morepartitions based on a current velocity of the mobile device. Forexample, the mobile device may select a partition with a smaller FFTsize when it is moving above a threshold velocity (or expects to moveabove the threshold velocity, has recently moved above the thresholdvelocity, etc.). In some embodiments, the mobile device may select apartition based on user input, e.g., whether to view local or regionalcontent. In some embodiments, the mobile device may select a partitionbased on instructions from the broadcasting base station.

The selected one or more partitions may include one or more service datastreams, as variously described herein. In the case that the partitionincludes more than one service data stream, the user device may extractOFDM symbols from one or more of the service data streams for which ithas been granted permission to access. The base station may signal tothe user device which service data streams it is permitted to access,e.g., based on permission control information provided by the broadcastgateway.

Contrasts with DVB

Digital Video Broadcasting—Second Generation Terrestrial (DVB-T2includes a Future Extension Frame (FEF) as a mechanism to enable a mixedSuper Frame (SF) structure. According to DVB, the mixed Super Frame maypermit the same network to transmit in the same frequency band bothfixed and mobile TV services each with an optimized waveform (i.e. timesegmented transmission of T2 and FEF frames).

To preserve backward compatibility, DVB-T2 imposes several constraintslisted as follows to allow the introduction of FEFs.

-   -   The ratio of T2 frames to FEFs is fixed and is repeated inside a        SF.    -   An SF should start with a T2-frame and should end with a FEF.    -   It is not possible to have 2 consecutive FEFs.

The present disclosure imposes no such constraints. For example:

-   -   The ratio of transport resources allocated between FFT modes        (and respective partitions) is determined statistically, in some        embodiments, based on the respective configuration in each mode,        i.e. FFT size, CP duration, and payload extent in symbols.    -   There are no restrictions on the FFT mode inserted at either the        start or end of a frame, in some embodiments.    -   The FFT modes will repeat in succession as needed to satisfy the        statistical multiplexing arrangement, in some embodiments.

The present disclosure further permits the option to separate partitionsin the frequency domain, i.e., confining each partition to separate setsof subcarriers. This is a capability not readily addressable within DVB.

Efforts to merge different FFT modes within a single DVB frame wouldrequire a change in the preamble structure, undermining backwardcompatibility with legacy receivers. Given the manner in which framesare multiplexed in DVB, confined to separate P1 preamble regions, thereis no gain in time diversity. Restrictions imposed on the ratio of T2 toFuture Extension Frames limits the usefulness of this DVB multiplexingarrangement to a limited set of hand-crafted use case scenarios.

Any of the various embodiments described herein may be realized in anyof various forms, e.g., as a computer-implemented method, as acomputer-readable memory medium, as a computer system, etc. A system maybe realized by one or more custom-designed hardware devices such asApplication Specific Integrated Circuits (ASICs), by one or moreprogrammable hardware elements such as Field Programmable Gate Arrays(FPGAs), by one or more processors executing stored programinstructions, or by any combination of the foregoing.

In some embodiments, a non-transitory computer-readable memory mediummay be configured so that it stores program instructions and/or data,where the program instructions, if executed by a computer system, causethe computer system to perform a method, e.g., any of the methodembodiments described herein, or, any combination of the methodembodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets.

In some embodiments, a computer system may be configured to include aprocessor (or a set of processors) and a memory medium, where the memorymedium stores program instructions, where the processor is configured toread and execute the program instructions from the memory medium, wherethe program instructions are executable to implement any of the variousmethod embodiments described herein (or, any combination of the methodembodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets). Thecomputer system may be realized in any of various forms. For example,the computer system may be a personal computer (in any of its variousrealizations), a workstation, a computer on a card, anapplication-specific computer in a box, a server computer, a clientcomputer, a hand-held device, a mobile device, a wearable computer, asensing device, a television, a video acquisition device, a computerembedded in a living organism, etc. The computer system may include oneor more display devices. Any of the various computational resultsdisclosed herein may be displayed via a display device or otherwisepresented as output via a user interface device.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

What is claimed is:
 1. An apparatus, comprising: one or more processingelements configured to: receive, via a wireless radio, wireless datathat includes: a plurality of portions that each include multiplesymbols, wherein different ones of the portions have different frequencytransform sizes and different cyclic prefix sizes; and control data thatindicates respective frequency transform sizes and cyclic prefix sizesfor the ones of the portions; select, based on the control data, one ormore but not all of the plurality of portions; and decode the selectedone or more portions to determine data represented by the symbols in theselected one or more portions.
 2. The apparatus of claim 1, wherein theselection of the one or more of the plurality of portions is furtherbased on a range of the apparatus from a transmitter of the wirelessdata.
 3. The apparatus of claim 1, wherein symbols in different ones ofthe portions have different time lengths in the time dimension.
 4. Theapparatus of claim 1, wherein different ones of the portions havedifferent sampling rates.
 5. The apparatus of claim 1, wherein thedifferent frequency transform sizes are different Fast Fourier Transform(FFT) sizes.
 6. The apparatus of claim 1, wherein ones of the portionsare different frames of wireless data.
 7. The apparatus of claim 1,wherein the portions are divided in at least one of the time dimensionor the frequency dimension.
 8. A method, comprising: receiving orgenerating, by a computing system: payload data for one or moretransmissions of wireless data, wherein the payload data includes aplurality of portions that each include multiple symbols, whereindifferent ones of the portions have different frequency transform sizesand different cyclic prefix sizes; and control data that indicates thefrequency transform sizes and cyclic prefix sizes for the ones of theportions; and causing, by the computing system, the payload data and thecontrol data to be wirelessly broadcast.
 9. The method of claim 8,wherein a first one of the plurality of portions is adapted for decodingby receivers at distances in a first range of distances and wherein asecond one of the plurality of portions is adapted for decoding byreceiver at distances in a second, different range of distances.
 10. Themethod of claim 9, wherein the second one of the plurality of portionshas a different cyclic prefix size than the first one of the pluralityof portions.
 11. The method of claim 8, wherein a first one of theplurality of portions is adapted for decoding by mobile devices movingat velocities up to a first maximum velocity and wherein a second one ofthe plurality of portions is adapted for decoding by mobile devicesmoving at velocities up to a second, different maximum velocity.
 12. Themethod of claim 8, wherein different ones of the portions have differentsampling rates.
 13. The method of claim 8, wherein the differentfrequency transform sizes are different Fast Fourier Transform (FFT)sizes.
 14. The method of claim 8, wherein the ones of the portions areincluded in the same frame of wireless data.
 15. The method of claim 8,wherein the portions are divided in at least one of the time dimensionor the frequency dimension.
 16. A non-transitory computer-readablemedium having instructions stored thereon that are executable by anelectronic device to perform operations comprising: receiving a frame ofbroadcast wireless data that includes: a plurality of portions that eachinclude multiple symbols, wherein different ones of the portions havedifferent frequency transform sizes and different cyclic prefix sizes;and control data that indicates respective frequency transform sizes andcyclic prefix sizes for the ones of the portions; selecting, based onthe control data, one or more but not all of the plurality of portions;and decoding the selected one or more portions to determine datarepresented by the symbols in the selected one or more portions.
 17. Thenon-transitory computer-readable medium of claim 16, the selecting isfurther based on a range of the electronic device from a transmitter ofthe wireless data.
 18. The non-transitory computer-readable medium ofclaim 16, wherein the different frequency transform sizes are differentFast Fourier Transform (FFT) sizes.
 19. The non-transitorycomputer-readable medium of claim 16, wherein ones of the portions aredifferent frames of wireless data.
 20. The non-transitorycomputer-readable medium of claim 16, wherein the portions are dividedin at least one of the time dimension or the frequency dimension.